The invention relates to an electromagnetic device for position measurements of the type.
Such an electromagnetic device is known from German Offenlegungsschrift 27 32 950. According to this publication, there are provided both for the transmitter and for the receiver in each case three coils perpendicular to one another which are operated with currents of the same frequency, which are dephased relative to one another by 90.degree., and by means of a stage of differing frequency. In this way, voltages are induced in the receiver which experience amplification, rectification, summation and further processing. The axes of the coils may coincide at one point, but be also disposed offset to one another. A coil cross disposed on one plane may be enclosed by an enveloping coil having an axis perpendicular thereto. By means of an arrangement comprising a receiver and a transmitter, the distance of the probes from one another should thereby be continuously detected independently of torsion and in a contact-free manner.
Range measurements undertaken with the known probe can, however, only be evaluated at close-range for distances between 1 to 21 cm. Beyond this range, the measured values are no longer meaningful. The measuring results are moreover sensitive with regard to the angular position of the probes relative to one another. Angle variation measurements undertaken without range measurements show for these probes a high degree of spread, with anisotropy additionally superimposed, so that measurements of the relative angular position cannot be evaluated.